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1. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 11 | Nov 2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 933
Under Water Optical Wireless Communication
RPVG Ashok Reddy1, J Rajani Kanth2, D Muneendra
1,3Assistant Professor, Dept of ECE, SIETK, Andhra Pradesh, India
2Associate Professor, Dept of ECE, SIETK, Andhra Pradesh, India
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Abstract - Underwater absorption, scattering and
turbulence processes will introduce attenuation and fading to
light propagation and then degrade the performance of
underwater wireless optical communications (UWOC). As
power consumption is an important issue in under- water
missions, it is fundamental to minimize the intensity loss by
reducing the beam divergence , data transmission inrelatively
high turbidity waters appeals for the use of energy-efficient
modulations and powerful channel codes at the physical and
data link layers. The particular difficulty of developing such
model resides in the fact that turbulencehighly dependsonthe
operational scenario and also on the water conditions
underwater wireless optical communications (UWOC), pulse
modulation technique has been widely used due to the high
optical power efficiency and relatively low system complexity.
Compared with the simplest on-off keying (OOK) scheme,
digital pulse interval modulation(DPIM)improvesbothpower
efficiency and error performance and requires no symbol
synchronization. Polarization shift keying (Polk) is another
appropriate modulation scheme whichcaneffectivelyrestrain
background noise. A scheme named, polarizedDPIM(P-DPIM)
and Po1SK , combining both to further improve the
performance, and deriving its bit-error- rate(BER)expression
in additive white Gaussian noise (AWGN) channel. UWOC
channel suggest that P-DPIM scheme can improve both the
power efficiency and error performance as well as
communication distance compared with traditional PPM and
DPIM schemes.
Key Words: Underwater wireless optical communications
(UWOC), pulse modulation technique, digital pulse interval
modulation (DPIM), on-off keying (OOK) scheme, polarized
DPIM (P-DPIM), Polarization shift keying (Polk).
1. INTRODUCTION
An optical fiber (or fibre) is a glass or plastic fiber that
carries light along its length. Fiber optics is the overlap of
applied science and engineering concerned with the design
and application of optical fibers. Optical fibers are widely
used in fiber-optic communications, which permits
transmission over longer distances and at higher
bandwidths (data rates) than other forms of
communications. Fibers are used instead of metal wires
because signals travel along them withlessloss,andtheyare
also immune to electromagnetic interference.Fibersarealso
used for illumination, and are wrapped in bundles so they
can be used to carry images, thus allowing viewing in tight
spaces. Specially designed fibers are used for a variety of
other applications, including sensors and fiber lasers.
In fibers, there are two significant sections– thecoreandthe
cladding. The core is part where the light rays travel and the
cladding is a similar material of slightly lower refractive
index to cause total internal reflection. Usually bothsections
are fabricated from silica (glass). The light within the fiberis
then continuously totally internally reflected along the
waveguide.
When light enters the fiber we must also consider refraction
at the interface of the air and the fiber core. The difference in
refractive index causes refraction of the ray as it enters the
fiber, allowing rays to enter the fiber atananglegreaterthan
the angle allowed within the fiber as shown in the figure.
An optical fiber transmission link comprises theelements as
shown in fig. The key sections are a transmitter consisting of
a light source and its associated drive circuitry, a cable
offering mechanical and environmental protection to the
optical fibers contained inside, and a receiver consisting ofa
photo detector plus Amplification and signal- restoring
circuitry. Additional components includeoptical connectors,
splices, couplers or beam splitters,andrepeaters.Thecabled
optical fiber is one of the most important elements in an
optical fiber link.
2. OPTICAL WIRELESS COMMUNICATION
Optical wireless communications (OWC) is a form of optical
communication in which unguided visible, infrared (IR), or
ultraviolet (UV) light is used to carry a signal.
OWC systems operating in the visible band (390–750 nm)
are commonly referred to as visible light communication
(VLC). VLC systems take advantage of light emitting diodes
(LEDs) which can be pulsed at very high speeds without
noticeable effect on the lighting output and human eye. VLC
can be possibly used in a wide range of applications
including wireless local area networks, wireless personal
area networks and vehicular networksamongothers.Onthe
other hand, terrestrial point-to-point OWC systems, also
known as the free space optical (FSO)systems,operateat the
near IR frequencies (750–1600nm).Thesesystemstypically
use laser transmitters and offer a cost-effective protocol-
transparent link with high data rates, i.e., 10 Gbit/s per
wavelength, and provide a potential solution for the
backhaul bottleneck. There has also been a growing interest
on ultraviolet communication (UVC) as a result of recent
progress in solid state optical sources/detectors operating
within solar-blind UV spectrum (200–280 nm). In this so-
called deep UV band, solar radiation is negligible at the
ground level and this makes possible the design of photon-
counting detectors with wide field-of-view receivers that

2. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 11 | Nov 2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 934
increase the received energy with little additional
background noise. Such designs are particularly useful for
outdoor non-line-of-sight configurations to support low
power short-range UVC such as in wireless sensor and ad-
hoc networks.
3. Block Diagram
4. Simulation Set-up and Results
The simulation is done using OptiSystem Simulation
Software. OptiSystem is a thorough programming outline
suite that empowers to arrange, test, and rebuild optical
connections in cutting edge optical systems. Propose
algorithm comprises of a transmitter with RZ signals,
wireless optical channel, optical receiver consisting of PIN
photodetector, Bessel filter and BER analyzer to analyze the
yield result. The biggest challenge for underwater wireless
communication originates from the fundamental
characteristics of ocean or sea water; addressing these
challenges requires a thorough understanding of complex
physio-chemical biological systems. So as to investigate the
effect of nonlinearitiesonthe optical communicationsystem,
the transmission distance of the optical system is differed.
The length of the wireless optical channel is differed. To
produce the optical signs we have utilized a CWlasersource,
Mach-Zehnder modulators, RZ signal generator and a
sinusoidal electrical sign generator.
Table1: Simulation Parameters
Parameters Values
Bit Rate 40 Gbps
Modulation RZ
Distance (km) 10, 20, 30, 40,50 km
Power 1 mw
Wavelength 1550 nm
4. Results & Discussion
We have simulated the optical link working at 10 Gbps. The
nonlinear effects are analyzed in terms Q Factor, BER with
the use of Eye Diagrams. Followingtableshowstheimpactof
nonlinear effects on the Q-factor in accordance to the
increase in transmission distance for RZ modulation.
Table2: Q Factor Vs Distance
Factors Distance (Km)
10 20 30 40 50
Q-factor 102.25 42.7 4 22.5012 14.2636 9.7028
BER 0 0 1.9E- 112 1.79E- 46 1.14E- 022
The below figures (a) & (b) shows the eyediagramofthelink
at 10 km and 50km respectively.

3. International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056
Volume: 05 Issue: 11 | Nov 2018 www.irjet.net p-ISSN: 2395-0072
© 2018, IRJET | Impact Factor value: 7.211 | ISO 9001:2008 Certified Journal | Page 935
It can be seen from the result that as the distance increases
the output in terms of Q-factor and eye diagram decreases.
5. Conclusion
As power consumption is an importantissueinunder-water
missions, it is fundamental to minimize the intensity loss by
reducing the beam divergence , data transmission in
relatively high turbidity waters appeals for the use of
energy-efficient modulations and powerful channel codes at
the physical and data link layers. In this paper underwater
wireless optical link is generated using optisystemsoftware.
The link is simulated for 10 km to 50 km and the distortions
are taken into consideration. It can be seen from the result
that as the distance increases theoutputgetsmoredistorted.
The output is better at 10 km compared to 50 km in terms of
Q-factor, Bit Error Rate and eye Diagram.
6. References
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1-4673-2733-6,2012.
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[3] Hai-Han Lu1, Chung-Yi Li1, Hung-Hsien Lin1, Wen-Shing
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[4] Yuhan Dong, Jinxing Liu ― “On BER Performance of
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[5] Xuelong Mi and Yuhan Dong ― “Polarized Digital Pulse
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